The present disclosure relates to a locking mechanism for movable units incorporated in image forming apparatuses such as electrophotographic copiers and laser printers, and relates also to sheet feeding devices and image forming apparatuses incorporating such a locking mechanism.
Conventionally, images forming apparatuses such as electrophotographic copiers and laser printers are provided with replaceable units that are removable from the image forming apparatuses main body, such as a drum unit which incorporates a photosensitive drum, a charging device, and a cleaning device, a developing unit which supplies toner to a photosensitive drum and develops an electrostatic latent image to form a toner image, and a toner cartridge which feeds toner to a developing unit. In these structures, a locking mechanism is provided so that the replaceable units do not disengage from the image forming apparatus main body except when necessary.
Other than for replaceable units, a locking mechanism is provided also for movable members that are pivotably provided relative to the image forming apparatus main body, such as a conveying unit, an exterior cover, or the like, so that the movable members do not pivot except when necessary.
For example, there is known a sheet feeding apparatus provided with a sheet feed tray and an apparatus main body. The sheet feed tray includes a lever which is integrally fitted to the sheet feed tray and which is operated substantially in the horizontal direction to permit the sheet feed tray to be inserted and extracted, and a hook which is engaged with the lever and can pivot as the lever is operated. The apparatus main body includes a first biasing member which applies pressure in such a direction as to push the sheet feed tray out of the apparatus main body, a positioning member which engages with the hook to position the sheet feed tray relative to the apparatus main body, and a second biasing member which biases so as to apply pressure to the positioning member against the hook.
For another example, there is also known a sheet conveying device, where an upper guide that serves also as an exterior portion is coupled by a coupling member which is an elastic member provided on the lower guide fixed integrally to the frame of the apparatus main body. When the hook at an access portion is fixed by being locked on a stopper on the apparatus main body, if the horizontal moving range of the upper guide is equal to or larger than the gap between the access portion and the apparatus main body, elasticity of the coupling member helps fill the gap.